MAT 150 – AlgebraClass #11Topics:• Find the exact quadratic function that fits three points on a

parabola • Model data approximately using quadratic functions

Writing a Quadratic Function

• A parabola passes through the points (0, 5), (4, 13) and (-2, 25). Write the equation of the quadratic function whose graph is this parabola.

Speed vs. Fuel EconomyA study compared the speed x (in miles per hour) and the average fuel economy y (in miles per gallon) for cars. The results are shown in the table. Using the function, what is the fuel economy if the speed is 47?• Plot the data points. Is it linear or

quadratic? • Write the equation of this function.

Speed, x Fuel Economy, y

15 22.320 25.525 27.530 2935 28.840 3045 29.950 30.255 30.460 28.865 27.470 25.3(Source: Transportation Energy Data Book)

Quadratic RegressionUsing the pervious data, put the data into your calculator where Speed is List 1 and Fuel Economy is List 2

Now select STAT, CALC, 5: QuadReg

What is the fuel economy if the speed is 47?

When can we be certain that this model no longer applies?

How to use Excel

Modeling with Power Functions Years after 1950 Households (thousands)10 43920 52330 158935 198340 285645 366852 489854 508057 620958 6210

Plot the data points. Write the equation of this function.

How to use Excel

Assignment

Pg. 223-230#1 , 5 and 8#12, 15, 17, 20, 21#29, 35, 45, 48